1. Field of the Invention
The present invention relates to a polishing machining apparatus and a machining method for machining a workpiece to be polished where a plurality of magnetic heads are arranged, and more particularly to an apparatus and a method for correcting a bend of the workpiece during the machining work.
2. Related Background Art
A thin film magnetic head to be used in a magnetic disc apparatus or the like is composed of parts obtained by machining a rod-shaped ceramic (hereinafter referred to as a ceramic bar) where a number of element parts made of a magnetic thin film or the like forming induction type magnetic converting elements, magnetic resistors (hereinafter referred to as MRs) elements or the like are formed in a line on a surface. Conventionally, in a batch type manufacturing process of parts for the thin film magnetic head, the ceramic bar where the plurality of element portions are formed is polished, and a process for machining a throat height or an MR height of each element part to a suitable level is executed. In general, in the magnetic disc apparatus, in order to stabilize the output characteristics from the magnetic head, it is necessary to keep a distance between the magnetic polar portions of the magnetic head and a surface of a recording medium to an extremely narrow constant distance. The value of the throat height or the like is used as an important parameter for defining this distance.
In the following description, the throat height means a length (height) of the tip end portion of the magnetic poles for performing the recording/reproduction of magnetic signals in such a head core part, i.e., the portion where the two magnetic poles face each other at a fine gap. Also, the MR height means a length (height) from the end portion of the MR element on the side facing the medium to the opposite end portion thereof. In order to make it possible to perform the suitable recording/reproduction of the signals, the values of the throat height, the MR height and the like must be selected suitably. In order to obtain the predetermined values, high precision is needed for the polishing work.
The ceramic bar is to be cut into respective element portions in a process thereafter. Each of the element portions constitutes a part of a magnetic head for the magnetic disc apparatus. In the case where the magnetic head is used in the magnetic disc apparatus, the ceramic portion becomes a slider that is to be lifted away from the magnetic disc by the blow pressure caused by the rotation of the disc. The element portion becomes a head core for performing the recording and/or reproducing the magnetic signals of the disc.
However, in general, the above-described ceramic bar has a strain, a bend or the like due to the stress caused by the formation of the element portion or the cutting operation from the ceramic substrate. It is therefore difficult to obtain the high machining precision only by fixing the ceramic bar and effecting the polishing work thereon. For this reason, a non-general polishing apparatus for performing the polishing work of the magnetic head with high precision in the form of the ceramic bar as disclosed in, for example, U.S. Pat. No. 5,620,356 or the like has been proposed. Also, the present assignee proposes some apparatus and some methods (Japanese Patent Application No. 11-162799 or the like).
An actual polishing method for the above-described ceramic bar will now be described.
First of all, the surface opposite the polishing surface of the ceramic bar, is fixed with adhesives or the like to a jig, and the surface to be polished of the ceramic bar is depressed through the jig against the polishing surface of a polishing base to perform the polishing work to the surface to be polished. The jig has a beam structure. A load is applied to several, three to seven, specific points on the jig from the outside of the jig to thereby cause deformation in the jig as a whole. Furthermore, this beam structure allows the portions fixed to the ceramic bar to be subjected to the complicated deformation by the balance adjustment of the above-described load, and the ceramic bar is bent simultaneously with the fixed portions to thereby make it possible to correct the bend or the like owned by the ceramic bar per se.
In the polishing work, in a predetermined element portion on the ceramic bar fixed to the jig, the values such as a throat height are measured optically or electrically to thereby obtain the difference between the measurement value and the target value, i.e., the amount of polished portion needed upon the measurement. The loads at the plurality of points are adjusted on the basis of the necessary polishing amount in the predetermined element portion obtained and the portion in the vicinity of the predetermined element portion, and the ceramic bar is polished while being deformed through the jig. These steps are repeated whereby the values such as the throat height and the like of all the elements formed in the ceramic bar fall within the predetermined range.
Opening portions into which pins or the like may be inserted are formed in the beam portion of the jig. The loads to the jig in the above-described process are given by transmitting the loads due to an actuator such as a low friction cylinder to the pins inserted into the opening portions of the jig through transmission parts. The adjustment of the loads to the jig is performed by adjusting the loads from this actuator, i.e., a drive amount of the actuator. Incidentally, Japanese Patent Application No. 10-178949 filed by the present applicant discloses a specific example of a jig for causing an effective deformation or a load distribution to the ceramic bar.
In a recording density in the current magnetic disc apparatus or the like, it is possible to make the values such as a throat height fall within an allowable range to some extent by a machining method of the magnetic head using the above-described jig. However, the high recording density is accelerated, and recently, the high precision of the throat height or the miniaturization of the elements are remarkable. It is difficult to make the values such as the throat height fall within the allowable range over the full length of the ceramic bar.
In the case where the allowable range of the values such as the throat height is narrowed, there is an approach to cope with this by, for example, increasing the application points of the loads that cause the deformation in the jig. However, since this leads to the increase of the number of the actuators that actually apply the loads or the transmission portions (application points) of the loads, if the actuators or the like used in the conventional apparatus are needed, it is difficult to actually perform this approach since the space for mounting the actuators or the like would be increased remarkably in view of the structure of the polishing apparatus. Also, in the case where the jig per se is miniaturized in accordance with the miniaturization of the elements, there would be a problem in that it is difficult to arrange the necessary number of the actuators or the like for applying the loads to the application points of the necessary loads, and the like.
Furthermore, in the conventional polishing method, since the affect of the repulsive force from the polishing surface exists between the application point of the load and the beam or between the application points, it is impossible to sufficiently deform the ceramic bar. Accordingly, also in some conventional cases, depending upon the allowable range of the values such as a throat height, the values of the portion that may not be deformed could not fall within the allowable range. The approach to increase the number of the application points of the load and the number of the actuators for this problem has been attempted but there is a limit in the allowable range due to the above described problem.
Also, the conventional apparatus has three to seven actuators for deforming the jig in addition to the actuator for applying the main pressure for depressing the ceramic bar against the polishing surface and adjusting the load balance at both end portions in the longitudinal direction of the ceramic bar. However, actually, in order to bend the retainer portions to a necessary level, the three to seven actuators have to have a large stroke due to the necessary bend level and the actuators that always have the large stroke and occupy the large space in the structure are necessary as in the conventional case. Moreover, in order to make it possible to provide the complicated bend, the opening portion of the jig into which the pins cooperating with the actuators are inserted is increased to provide the form that may imparts a moment in the vertical direction, in the lateral direction and in the rotational direction with respect to the opening portion. In addition, it is necessary to effect the complicated drive control for each actuator. Accordingly, the conventional apparatus is not suitable for imparting the predetermined deformation amount to the very restricted portions of the ceramic bar.
In view of the above, an object of the present invention is to provide an apparatus that easily imparts a complicated bend deformation or the like to an object to be machined (polished) such as a ceramic bar by using an actuator having a small drive stroke in comparison with a conventional apparatus to make it possible to impart a depression force also to a specific portion whereby decreasing non-uniformity of a machining (polishing) amount of the object to be machined (polished) through the machining (polishing) process of the object to be machined (polished).
In order to solve this and other objects, according to the present invention, there is provided a machining apparatus for machining an object, elongated in one direction, to be machined, comprising: a machining base with a machining surface to be rotationally driven, a machining head mounted frame disposed movably to the machining surface, and a machining head supported by the machining head mounted frame, characterized in that the machining head includes a jig for holding the object to be machined, an up-and-down moving portion moving up and down relative to the machining surface together with the jig, and a correcting mechanism supported by the up-and-down moving portion, the correcting mechanism includes a base fixed to the up-and-down moving portion, a plurality of levers each of which has a pin at one end, a shaft fixed to the base for rotatably supporting the levers, and a plurality of correcting drive means coupled to other ends of the levers for pivoting the levers with respect to the shaft to thereby pivot the pins, the jig includes a body portion fixed to the up-and-down moving portion, a holding portion elongated in one direction and fixed to the body portion for holding the object to be machined, and a plurality of load receiving portions arranged in parallel in the one direction on the holding portion, and the load receiving portions receive the pins and are driven in accordance with the pivotal movement of each pin whereby portions corresponding to the load receiving portion in the holding portion are deformed together with the object to be machined.
Also, according to the present invention, it is preferable that tip ends of the pins are substantially spherical. It is preferable that the adjacent levers each have different lengths from each other, and distances between the plurality of correcting drive means and the shaft are different from each other in accordance with a length of the levers. Also, it is preferable that the shaft supports the levers in a position in the vicinity of the pins and the correcting drive means are REC plungers.
Furthermore, in order to attain the above-noted object, according to the present invention, there is provided a machining apparatus for machining an object, elongated in one direction, to be machined, comprising: a machining base with a machining surface to be rotationally driven, a machining head mounted frame disposed movably to the machining surface, and a machining head supported by the machining head mounted frame, characterized in that the machining head includes a jig for holding the object to be machined, an up-and-down moving portion moving up and down relative to the machining surface together with the jig, and a correcting mechanism supported by the up-and-down moving portion, the correcting mechanism includes a base fixed to the up-and-down moving portion, a plurality of correcting drive means each of which is fixed at an end to the base, a shaft coupled coaxially with the correcting drive means, and pins projecting from the shaft, the jig includes a body portion fixed to the up-and-down moving portion, a holding portion elongated in one direction and fixed to the body portion for holding the object to be machined, and a plurality of load receiving portions arranged in parallel in the one direction on the holding portion, and the load receiving portions receive the pins and are driven in accordance with the movement of each pin whereby portions corresponding to the load receiving portion in the holding portion are deformed together with the object to be machined.
Furthermore, in order to attain the above-noted object, according to the present invention, there is provided a machining apparatus for machining an object, elongated in one direction, to be machined, comprising: a machining base with a machining surface to be rotationally driven, a machining head mounted frame disposed movably to the machining surface, and a machining head supported by the machining head mounted frame, characterized in that the machining head includes a jig for holding the object to be machined, an up-and-down moving portion moving up and down relative to the machining surface together with the jig, and a correcting mechanism supported by the up-and-down moving portion, the correcting mechanism includes a base fixed to the up-and-down moving portion, a plurality of substantially frame-like members fixed to the base, a plurality of correcting drive means held on centerlines of the substantially frame-like members, and a plurality of shafts extending in parallel with a drive direction of the correcting drive means, coupled at first ends with the substantially frame-like members and provided at the other ends with pins, the jig includes a body portion fixed to the up-and-down moving portion, a holding portion elongated in one direction and fixed to the body portion for holding the object to be machined, and a plurality of load receiving portions arranged in parallel in the one direction on the holding portion, and the load receiving portions receive the pins and are driven in accordance with the movement of each pin whereby portions corresponding to the load receiving portion in the holding portion are deformed together with the object to be machined.
Also, according to the present invention, it is preferable that tip ends of the pins are substantially spherical and the adjacent shafts each have different lengths from each other, and distances between the correcting drive means and the pins are different from each other in accordance with a length of the shafts. Also, according to the present invention, it is preferable that the shafts are arranged coaxially with the correcting drive means and the correcting drive means are piezoelectric element actuators.
Furthermore, in order to attain the above-noted object, according to the present invention, there is provided a machining apparatus for machining an object, elongated in one direction, to be machined, comprising: a machining base with a machining surface to be rotationally driven, a machining head mounted frame disposed movably to the machining surface, and a machining head supported by the machining head mounted frame, characterized in that the machining head includes a jig for holding the object to be machined, an up-and-down moving portion moving up and down relative to the machining surface together with the jig, and a correcting mechanism supported by the up-and-down moving portion, the correcting mechanism includes a plurality of shafts provided at ends with pins and having convex portions different from the pins, a pair of correcting drive members disposed on one line on both sides of the convex portions and clamping the convex portions, and a base fixed to the up-and-down moving portion with recess portions receiving the pair of correcting drive member and the convex portions, the pair of correcting drive members drive the convex portion in a straight line to drive the shafts and the pins in parallel with the straight line, the jig includes a body portion fixed to the up-and-down moving portion, a holding portion elongated in one direction and fixed to the body portion for holding the object to be machined, and a plurality of load receiving portions arranged in parallel in the one direction on the holding portion, and the load receiving portions receive the pins and are driven in accordance with the movement of each pin whereby portions corresponding to the load receiving portion in the holding portion are deformed together with the object to be machined.
Also, according to the present invention, it is preferable that tip ends of the pins are substantially spherical and sizes of projections of the adjacent convex portions are different from each other and the arrangement of the correcting drive members each received in the recess portion and a size of the recess portions are defined in accordance with the sizes of the convex portions. Also, according to the present invention, it is preferable that the pair of correcting drive members have a pair of pistons to be driven by pressure medium, and the base has a pair of pressure medium introduction ports in communication with a rear portion of each of the pair of pistons and the pair of adjacent pressure medium introduction ports are each arranged at different distances from a predetermined surface of the base.
Also, according to the present invention, it is preferable that one of the pair of correcting drive members has a piston to be driven by pressure medium, the other being formed of elastic member, and the base has a pressure medium introduction port in communication with a rear portion of the piston. Also, it is preferable that the pair of adjacent pressure medium introduction ports are each arranged at different distances from a predetermined surface of the base. Also, it is preferable that the pressure medium is pressurized air.
Furthermore, in order to attain the above-noted object, according to the present invention, there is provided a machining apparatus for machining an object, elongated in one direction, to be machined, comprising: a machining base with a machining surface to be rotationally driven, a machining head mounted frame disposed movably to the machining surface, and a machining head supported by the machining head mounted frame, characterized in that the machining head includes a jig for holding the object to be machined, an up-and-down moving portion moving up and down relative to the machining surface together with the jig, and a correcting mechanism supported by the up-and-down moving portion, the correcting mechanism includes a shaft, a plurality of levers composed of linear portions provided at ends with pins and supported rotatably by the shaft at portions different from the pins and driven portions coupled at end portions with the linear portions having convex portions, a pair of correcting drive members disposed in a linear manner on both sides of the convex portions while clamping the convex portions, and a base having recess portions for receiving the pair of correcting drive members and the convex portions and fixed to the up-and-down moving portion, the pair of correcting drive members drive in the linear manner to thereby drive the convex portion clamped thereby, whereby the levers and the pins are pivoted about the shaft, the jig includes a body portion fixed to the up-and-down moving portion, a holding portion elongated in one direction and fixed to the body portion for holding the object to be machined, and a plurality of load receiving portions arranged in parallel in the one direction on the holding portion, and the load receiving portions receive the pins and are driven in accordance with the pivotal movement of each pin whereby portions corresponding to the load receiving portion in the holding portion are deformed together with the object to be machined.
Also, according to the present invention, it is preferable that tip ends of the pins are spherical and it is preferable that sizes of projections of the adjacent convex portions are different from each other and the arrangement of the correcting drive members each received in the recess portion and a size of the recess portions are defined in accordance with the sizes of the convex portions. It is also preferable that the pair of correcting drive members have a pair of pistons to be driven by pressure medium, and the base has a pair of pressure medium introduction ports in communication with a rear portion of each of the pair of pistons. It is preferable that the pair of adjacent pressure medium introduction ports are each arranged at different distances from a predetermined surface of the base.
Also, it is preferable that one of the pair of correcting drive members has a piston to be driven by pressure medium, the other being formed of elastic member and the base has a pressure medium introduction port in communication with a rear portion of the piston. Its preferable that the pair of adjacent pressure medium introduction ports are each arranged at different distances from a predetermined surface of the base. Also, it is preferable the pressure medium is pressurized air and tip end portions of the pistons are substantially spherical.
Furthermore, according to the present invention, it is preferable that the jig has an electrode to be connected to an electric element formed on the object to be machined, and the correcting mechanism has a probe unit to be brought into contact with the electrode. Also, according to the present invention, it is preferable that the machining head has a balancing actuator, the jig has through holes in a central portion and both end portions in the longitudinal direction of the body portion, the jig is supported by the correcting mechanism by a fixing pin passing through the through hole in the central portion, and the jig is depressed to a direction toward the machining surface through the positioning pins at both end portions by the balancing actuator.
Also, according to the present invention, it is preferable that the machining head is supported through an adjust ring supported by the machining head mounting frame and in contact with the machining surface, and an angle of the machining head supported by the machining head mounting frame facing the machining surface is defined by the adjust ring. Also, it is preferable that the machining head is mounted rotatably to rails for mounting the machining head. Furthermore, it is preferable that the apparatus according to the invention further comprises a machining head swinging means, in which the machining head swinging means performs reciprocating rotational motion of the machining head within a predetermined angular range. It is more preferable that the object to be machined is a rod-like ceramic provided with a plurality of magnetic heads.
Furthermore, in order to attain the above-noted object, according to the present invention, there is provided a method for machining an object, to be machined, elongated in one direction by holding the object to be machined to a jig, and depressing the object to be machined to a machining surface formed in a machining base that is rotationally driven, through the jig, comprising the steps of: measuring a machining amount at a plurality of positions of the object to be machined when the object to be machined is depressed against the machining surface; and rotating a plurality of levers having pins at ends, together with the pins by a plurality of correcting drive means on the basis of the measured machining amount for imparting a predetermined deformation to the object to be machined together with the jig by the rotation of the pins with tip ends received in the jig.
Furthermore, in order to attain the above-noted object, according to the present invention, there is provided a method for machining an object to be machined, elongated in one direction by holding the object to be machined to a jig, and depressing the object to be machined to a machining surface formed in a machining base that is rotationally driven, through the jig, comprising the steps of: measuring a machining amount at a plurality of positions of the object to be machined when the object to be machined is depressed against the machining surface; and driving a plurality of shafts, disposed on the same axes with a plurality of correcting drive means and having pins, on the basis of the measured machining amount for imparting a predetermined deformation to the object to be machined together with the jig by the drive along the axes of the pins with tip ends received in the jig.
Furthermore, in order to attain the above-noted object, according to the present invention, there is provided a method for machining an object to be machined, elongated in one direction by holding the object to be machined to a jig, and depressing the object to be machined to a machining surface formed in a machining base that is rotationally driven, through the jig, comprising the steps of: measuring a machining amount at a plurality of positions of the object to be machined when the object to be machined is depressed against the machining surface; and driving a plurality of shafts having pins linearly by a pair of correcting drive means disposed on a plurality of straight lines on the basis of the measured machining amount and imparting a predetermined deformation to the object to be machined together with the jig by the drive on the straight lines of the pins with tip ends received in the jig.